Using C. elegans as a simple in vivo model, the developmental assembly of hemidesmosome (HD) and intermediate filament (IF) organization is being investigated. The epidermis contains a stress resistant network of IFs through which force can be transmitted. Mutations in mua-2, mua-3, mua-5, and mua-6 all result in a growth and use-dependent fragility of this HD/IF mediated trans-epithelial force transmission pathway. Two of these genes, mua-6 and mua-3, have been cloned and encode an IF and a HD associated protein, respectively. The other two genes, mua-5, and mua-2 whose products are as yet unidentified, have been shown to affect the integrity of these same epidermal complexes. These genes may have human homologues that are involved in the etiology of human diseases, but more importantly, the proposed research continues to develop a simple genetic model in which the biology of matrix receptors, cell adhesion, and their control in development can be studied, impacting on our basic understanding of these interactions in normal development and how they may go awry to cause misattachment or attachment failure in muscular dystrophies, blistering skin diseases and cancers. The long term objective is to understand the cell and molecular biology of HD and IF assembly in growth and development. The short term objective is to ascertain the molecular identity of the products of mua-5 and mua-2 and to understand the potential roles played by them in epidermal tissue integrity and the development of HD/IF complexes. The specific aims are: 1) Clone and identify the predicted products of mua-5, and mua-2 using positional rescue, 2) to identify the cellular and sub-cellular localization of MUA-5 and MUA-2 using GFP fusion constructs and antibodies, 3) to examine the localization of HD associated proteins in mua-2 and mua-5, as well as selected other mutants, and the colocalization of these proteins and MUA-2 and MUA-5 using antibodies and GFP reporters.